In enterprises etc., data in a storage device are periodically copied (backed up) on a volume-by-volume basis (on a per logical disk device basis), however, it is better to accept a read/write request for the volume even during copying the volume.
Further, when copying the volume, a copy of the data in the volume at a point of time when starting the copy must be generated. Therefore, a copy process for copying the volume is a process of copying, when receiving the write request to a storage area with the copy being not yet completed during copying the volume, the data to be rewritten due to the write request to at first a copy destination volume.
Specifically, the copy process involves, as schematically illustrated in FIG. 1, interrupting the copy of the data when receiving a write request 51 to the storage area with the copy being not yet completed during copying the copy source volume. The copy process further involves copying the data on a storage area 52, to which the data are requested by the write request 51 to be written, to a corresponding storage area 52′ of a copy destination volume, and thereafter making a response to the write request 51. Note that the phrase “making the response to the write request 51” implies “writing the data requested by the write request 51 to be written to the storage area 52 and thereafter sending a write completion response to a host.”
Thereafter, the copy process involves resuming the interrupted copy of the data (a process of copying only the not-yet-copied data of the copy source volume to the copy destination volume).
Note that the copy process involves, when receiving the write request to the already-copied storage area of the copy source volume/read request to the copy source volume, temporarily interrupting the copy of the data and resuming the copy of the data after making the response to the write request/read request. Further, the following are documents pertaining to copy (backup)-related technologies.